Effect of Iron and Silicon Impurities on Phase Composition and Mechanical Properties of Al–6.3Cu–3.2Y Alloy

Abstract–The effect of impurities of iron and silicon on the phase composition and mechanical properties of the Al–6.3Cu–3.2Y wrought aluminum alloy is investigated in this work. According to the results of X-ray diffraction of the cast alloy, the presence of Al₈Cu₄Y, (Al,Cu)₁₁Y, Al₂Cu, and AlCu phases was confirmed, and the presence of peaks that likely correspond to the Al₁₁Cu₂Y₂Si₂ phase was noted. Elongated needle-like inclusions of the Al₁₁Cu₂Y₂Si₂ phase, which does not change its morphology in the course of homogenization, appear against the background of the fragmented compact eutectic. At the temperatures of annealing of the deformed sheets up to 300°C, the structure of alloy is represented by grains elongated along the rolling direction and has a slightly higher hardness than the same alloy without impurities. This is caused by the presence of larger amount of sufficiently dispersed intermetallic particles in the structure. When increasing the annealing temperature, the difference in hardness between the considered alloys decreases. Recrystallization occurs starting from 350°С, the hardness of the alloys levels out. After annealings at 100 and 150°C, the studied alloy demonstrates a good level of strength characteristics, the conditional yield stress is 284–325 MPa, the conditional ultimate strength is 304–369 MPa, which is 20–30 MPa higher than in the alloy without impurities. In general, the presence of permanent impurities of iron and silicon in aluminum does not have a negative effect on the mechanical properties of the studied alloy.